Colloidal silica grouting is a mineral grouting (as opposed to chemical grouting) process primarily used for water control below grade. These grouts are exceptionally low viscosity (below 10 centipoise), whose reaction profiles can be controlled onsite. Colloidal silica grout does not expand. Colloidal silica grouts are hydrophilic. Cured colloidal silica grout is primarily water. Therefore, this type of grout is best for use in damp or wet environments.
Colloidal silicas are different from sodium silicates, but used in similar applications where very low grout viscosity is important.
Composition
The following components make up colloidal silica grouts:
- resin
- water
- salts, to control set time
The ratio of resin to water controls the consistency of the finished product.
Straight resin pumped 1:1 with water will yield a gummy bear/cooked egg white consistency finished product. Non-cohesive soils treated with colloidal silica grouting are friable, non-permeable, and will typically stand on their own, but still be hand-excavatable.
Placement
Sodium silicate grouts can be pumped separately and mixed at the placement point continuously, or batched and then pumped as a single stream. Pumping method is generally means & methods and varies depends on site conditions, geology, and a host of other factors.
Colloidal silicate grouts do not expand, and are slightly more viscous than water. Their low viscosity allows them to be pumped relatively quickly, without fracturing the treatment zone. This type of grout will not permeate clays, but is excellent for silts and sands.
Typical Colloidal Silica Grouting Repairs
Sodium silicate grouts are excellent for permeation grouting of soils, binding them together, and significantly reducing their permeability. Unlike soils treated with single component polyurethane resins, soils grouted are generally easily hand excavatable. Compared to acrylic grouts, which are similar viscosity, soils treated with silica grout are generally more friable, but similar reductions in permeability.
Sodium silicate grouts are generally chosen because of their very low viscosity. Viscosities similar to water allow mineral grouts to penetrate very tight cracks, and also to follow very fine water flow channels. Colloidal silica’s exceptionally low viscosity also allows it to permeate soils very uniformly, unlike resins, which tend to fracture soils, resulting in non-uniform permeation. Uniform permeation is the key to thoroughly addressing water flows through soils.
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